OK guys, thanks for all your help and comments, all appreciated.

1. I removed backglass and checked and re installed switch plugs on the CPU bottom left hand corner.....all looked ok
2. No green fuzz from battery leakage
3. Small PCB on onside of machine door checked fine, reseated them
4. Pulled wires on the memory protector switch, no difference made.

The display works fine, it tells me that coin door is open when it is, I can use flippers to check high scores etc, scroll. The playfield is all lit ready to go. It's just that I can't operate the buttons which provide me with credits etc. Up until now it has worked a treat. So I can't actually play it at all.
I'm in Adelaide, I bought the machine from 240 Amusements in Melb and had it shipped over about 4-5 years ago. They have been very helpful to me, just on this occasion I'm stuck.

240 said to me (from memory) it could have something to do with it being earthed?? Not exactly sure if this is what he said but thought to mention it here in case it means anything to you guys.

The photo I have attached is from underneath the buttons, and the main wiring loom does look ok, these wires here were tucked in near the switches, i pulled them down to show them in the photo, there is no plug on the end of any of these black/orang wires so itdoesnt look like theyve come off anything? Although I do notice spots for where 3 plugs could go right near the buttons, you might see it in the picture.

Anyway, thanks everyone for their help, other than offering any further advice, do you know any technicians in Adelaide? Looks like a $10 problem to me that might cost me a lot more than that by the time I get someone out!